FMRI assessment of load based working memory in blast TBI and associated effects in FDG-PET signal

The incidence of traumatic brain injury (TBI) has increased in recent military combat operations due to increased usage of improvised explosive devices as well as better blast survivability from body armor. Sensitive clinical diagnostic tools for mild traumatic brain injury, including structural neuroimaging, are lacking. Further, there is still little known regarding the long term effects of blast TBI on the structure and functioning of the brain. Although many veterans with blast TBI report long term cognitive changes, these diagnostic methods rarely reveal brain changes that corroborate self-reported difficulties. Integrating multimodal neuroimaging may yield more detailed information about the specific sequelae of blast TBI. Functional activation patterns may provide valuable insight into the behavioral characteristics of the brain following blast injury that help explain the origin of lingering cognitive problems reported by veterans. The present study integrated fMRI indices of behavioral activation during an n-back task with resting state metabolic activation using PET in a sample of veterans with mild (n=20) and moderate (n=15) blast TBI and healthy controls (HC) (n=22). Results showed decreased activation of the working memory network in TBI subjects compared to HCs assessed at higher working memory loads. Additionally fMRI based working memory network activation was compared to baseline FDG-PET datasets which revealed an association between functional assessment of the working memory system and baseline metabolism.